Process for securing good electrical contact with crystalline cuprous oxide



,Patented- Mar. 11, 1930 I uN-rrsn STATES PATENT o FFICE- I WILLIAM THEODORE ANDERSON, JR, AND LESTER FLETCHER BTRD, OF NEWARK,

NEW JERSEY, ASSIGNORS T0 HANOVIA'CHEMICAL AND MANUFACTURING COM- PANY, OI NEWARK, NEW JERSEY, A CORPORATION OF NEW JERSEY raocnss iron sncumneeoon ELECTRICAL con'rao'r wrrn caYs rALLnm corneas i 4 oxrnn Ho Drawing.

This invention relates to a process for making electrical connections with or stalline cuprous oxide crystals either sing y or in multiple as for example to a layer of crystals 5 attached to a metallic surface. Electrical contact has been made in the past to cuprous oxide crystals in various Ways among which may be cited thatof mechanically pressing a piece of lead tightly against the crystals. Other metals have been triedv with more or less success in various schemes but this invention is of a newand novel method'for securing good electrical contact with such crystals and is described fully herein and set forth in the appended claims.

There .are certain qualifications that must be met by any contact making means. First, the contact must be good providing a low resistance electrical joint between a conductor and a crystal. Second, this contact or resistance must not be affected by normal temperature changes in the unit. Third, the contact must be permanent so that it will not change with age or use. Fourth, it must be in such a form that electrical conductors can be attached to the contact making means, for example, thin lead foil pressed against the crystal might make good contact with the crystal 1 but in itself'be a poor conductor or require special reca-utions in connecting a conductor to the oil. Fifth, where contact is made to a crystalline surface the contact making -means should be continuous in itself not requiring anadditional strip of metal to provide contact to a number of small pieces.

All of the requirements for a satisfactory contact making means have'been met in our invention. The contact with the crystals is made by a continuous layer of metal strongly attached to the crystal surface. This metal layer is a good conductorand may be pro- -vided, in sufiicient stren h so that a connec tion maybe readily sol ered' to it. Several methods are given for the production of layers of different kinds of metals. Acomplete description of our invention follows:

A. layer of metallic silver can be deposited on the crystalline oxide surface in an exactly similar manner to that 'used in the preparaac tion of silver backed glass mirrors. The

Application filed October 28, 1927. Serial No. 229,523.

clean' oxide surface is immersed in a silver salt solution properly prepared and a'proper quantity of a special reducing solution added. Metallic silver is precipitated from the solution upon the oxide surface forming a smooth continuous adherent layer upon the oxide.

Those acquainted with the art of chemistry understand that this is the method of depositing silver upon glass to make mirrors. The i exact nature of the solutions is not essential to this invention since they have been used and known for years in the various arts.

A layer of metallic copper can be formed on a crystalline cuprous oxide surface by the reduction of a copper salt with powdered iron. The powdered iron is dusted over the .clean oxide surface and the whole immersed in a solution of copper sulphate. The iron is dissolved in the solution precipitating metallic copper upon the oxide surface.

A layer of metallic copper can be formed on the crystalline cuprous oxide surface by reducing the outermost surface of the oxide itself. The oxide is made the cathode in an electrolyte consisting'of acidified ammonium sulphate and electric current passed from an electrically conducting but chemically inert anode through the electrolyte to the cathode. Chemical reduction of the outermost surface of the oxide results in producing a layer of metallic copper upon the surface of the oxide.

Satisfactory conducting surfaces can be formed on the crystalline cuprous oxide by electroplating processes. The oxide surface is made the cathodein a suitable electrolyte and current is passed from an anode, composed of the metal desired upon. the oxide surface, through the solution to the cathode. Electrolytes cannot be used which attack the copper oxide since both the metallic copper and the cuprous oxide must exist simultaneously in the electrolyte without being destroyed by chemical action. Nickel was deposited successfully from nickel ammonium sulphate solution slightly acidified with boric acid. Copper can be deposited from soluand other'common copper salt electrolytes.

One of the most successful methods of sevtions of mildly acid copper sulphate salts p curing a good metallic surface over the crystalline cup'rous oxide was a combination of plating and reduction. Acidified nickel ammonium sulphate was used for the electrolyte and sufiicient acid was added to act upon the cuprous oxide reducing it to copper. By depositing the nickel electrolytically simultaneously with the reduction of the surcrystals face oxide a layer of bronze was formed on the surface of the crystalline oxide. As soon as the surfaceof the oxide was covered with metal the reduction ceased and pure nickel was electroplated until the desired thickness was reac ed. These metal layers are sufliciently well attached to the cuprous oxide that wires may be soldered to the metal to form external electrical connections.

Although we have described our invention .in considerable detail as illustrating the best known embodiment, it will be understood that minor changes may be made without departin from the invention as defined in the appen ed claims.

We claim:

1. Process for the production of a continuous electrically conducting, adherent metallic la er strongly attached to a surface of crysta line cuprous oxide, by the electrolytic deposition of nickel from a suitable electrolyte with suitable electrodes,.circuit arrangement 7 and electric current supply.

2. Process for the production of a continuous electrically conducting, adherent metallic layer strongly attached to a surface of crystalline cuprous oxide, by the electrolytic reduction of the outermost surface of the copper oxide and simultaneous deposition-of metallic nickel which with the reduced copper form a bronze metallic layer.

This specification signed this twenty-fifth day of October, l927.

WILLIAM THEODORE ANDERSON, Jr. LESTER FLETCHER BIRD. 

